30-08-2014, 02:22 PM
Antennas for wireless LAN systems
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INTRODUCTION
Personal computer services
WLAN-possible and affordable to surf the web from your laptop without any wire connectivity.
The aim of this project is to design efficient and reliable broadband patch antennas showing signs of directivity leading to adequate area coverage and sufficient bandwidth usage.
Antennas for wireless LAN systems
Currently most commonly used WLAN system is the IEEE 802.11b system.
Many antenna designs are already present in the market that will successfully meet the broadband requirement. For example an Omni-directional discone antenna .
The Broadband antennas are required to be compact, low-profile, directive with high transmission efficiency and designed to be discreet.
Microstrip patch antennas are well suited for wireless LAN application
Foundations for Microstrip Design
A microstrip patch antenna is a radiating patch on one side of a dielectric substrate, which has a ground plane on the underside.
The radiation efficiency of the
patch antenna depends largely
on the permittivity (εr) of the
dielectric
OPERATIONS OF MICROSTRIP PATCH
Polarization types
Linear Polarization
Circular Polarization
Bandwidth
Feeding techniques
Substrate permittivity
PHASE 1
Resonant line method
The Resonant Line method is used due to its ease of implementation and the return of accurate approximations.
When a signal is fed
into the input port, the
gaps act as open circuits
and in turn set up zero
current at these points
RECTANGULAR PATCH
The purpose of manufacturing a rectangular narrowband patch was to gain some of the insights to the patch design process.
The linearly polarized narrowband antenna was designed to operate at 2.45 GHz with input impedance of 50 ohms, using G10 fiberglass substrate.
PHASE 2
Broadbanding schemes
Planar Multi-resonators.
Stacked Electromagnetically coupled patches.
Stacked Electromagnetically coupled patches.
RECTANGULAR BROADBAND ANTENNA
By changing individual dimensions it is possible
to tune the antenna to achieve the best possible
broadband solution.
It is hard to notice the difference caused by altering the dimensions of one parasitic element.
TRIANGULAR BROADBAND ANTENNA
. Triangular patches hold similar attributes as rectangular patches while covering using a smaller area.
The triangular patches also have wide half-power beam widths in both planes. Therefore it is suitable for hemispherical application
ISSUES TO CONSIDER FOR FUTURE RESEARCH
A major hurdle the project suffered from was the inability of the new PCB milling machine to produce high frequency PCB boards.
When removing the extra copper from the substrate, the machine removed significant amount of substrate, resulting in reduced height and also creating ripples along the substrate plane
The use of copper tapes meant there was no turn around period and allowed us to resize the dimensions quickly and test the difference.
In deciding to use the copper tape, the active decision was made to trade off accuracy for time.
For future research and project, it is strongly recommended that a substrate with stable εr be used.
FUTURE RECOMMENDATIONS
SUBSTRATE
CLOSER INPUT IMPEDANCE MATCH
REDUCTION IN REAL-ESTATE AREA
CIRCULARLY POLARIZED BROADBAND ANTENNAS
USE OF OTHER BROADBAND SCHEMES